One of Britain's most senior black politicians has called on parties to set targets for the number of ethnic minority MPs in the House of Commons.

Baroness Amos, who was educated at Birmingham and Warwick universities, was only the second black person to sit in the Cabinet, and the first black woman.

However, Britain could be left with an all-white Cabinet again if she is appointed to a senior United Nations post. Tony Blair has nominated her for the role of head of the UN development programme.

Paul Boateng, the Chief Secretary to the Treasury and the country's first black Cabinet Minister, is to step down as an MP at the next election to become High Commissioner to South Africa.

Speaking to The Birmingham Post, Baroness Amos said the Labour Government had made more progress than any other in providing opportunities for black and Asian politicians.

But Britain had not yet reached a "critical mass" which would allow Parliament to more accurately reflect society as a whole, she said.

In the West Midlands conurbation, 17 per cent of the population is black or Asian. However there is only one MP from a visible ethnic minority.

Born in Guyana as Valerie Amos, Baroness Amos completed a degree in sociology at Warwick University and a master's degree in cultural studies from Birmingham University.

She joined the Cabinet as International Development Secretary in 2003, replacing Birmingham MP Clare Short, before becoming Leader of the House of Lords later that same year.

She said: "We haven't yet got to what I would call a critical mass, in terms of the number of ethnic minorities at senior positions, be it at the public or private sector.

"We need to see more people coming through the political system.

"I certainly think we should consider setting targets for the number of ethnic minorities that we get into our national Parliament.

"The parties have to look at this very carefully and very seriously.

"There are a whole number of other things we should be looking at. We should be looking at mentoring systems, and ways of supporting people.

"You have individuals in ethnic minority communities who are very active in local politics. Not necessarily in their local council, although some are, but in issues which affect their local community.

"Translating that into a more sustained engagement with political institutions and how we manage to do that, and looking very carefully at why the transition doesn't happen, I think is something I think we have a responsibility to do."

However she did not favour all-ethnic minority short-lists, in the way that Labour has introduced all-women shortlists in some seats.

However, Labour had a record of providing opportunities for minority politicians it could be proud of, she said.

"The majority of ethnic minority MPs are ours, the majority of ethnic minority peers are ours, we are the first Government to have two black Cabinet Ministers, and we have had two other black Ministers in the form of David Lammy and Patricia Scotland."